App Store & iTunes Gift Cards can be used in the iTunes Store, Apple Books, or App Store. On the email, you'll find a code from a original gift card to redeem. The card code, once redeemed, will add the money to your account and you will can make buys on apps, games, music, movies, TV shows, books, and iCloud.

You can go to support.apple.com/giftcard, if you need help reedeming the code.